p-Coumaroyl Malate Derivatives of the Pandanus amaryllifolius Leaf and Their Isomerization

A novel p-coumaroyl dimethyl malate (1) was isolated from the Pandanus amaryllifolius leaf in addition to three known analogs of p-coumaroyl dimethyl malate (2-4), and their structures were elucidated by analysis of the spectroscopic data. The p-coumaroyl malate derivatives were isolated as a mixture of E and Z isomers. To determine the cause of isomerization, the p-coumaroyl malate isolated in this study was synthesized. We concluded that the Z isomer might be an artifact generated from the E isomer through purification steps.